This week, 4 Chemicals stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Sigma-Aldrich Corporation (SIAL) improves from a B to a A rating this week. Sigma-Aldrich Corporation is a life science and high technology company engaged in the development, production and distribution of high quality chemicals, biochemicals, and related equipment. For more information, get Portfolio Grader’s complete analysis of SIAL stock.

This week, Agrium Inc. (AGU) pushes up from a C to a B rating. Agrium Inc. is a major retail supplier of agricultural products and services in the Americas, as well as a global producer and marketer of agricultural nutrients and industrial products. For more information, get Portfolio Grader’s complete analysis of AGU stock.

This week, Orion Engineered Carbons SA’s (OEC) ratings are up from a C last week to a B. The company also gets A’s in earnings momentum and return on equity. For more information, get Portfolio Grader’s complete analysis of OEC stock.

FutureFuel Corp. (FF) earns a B this week, jumping up from last week’s grade of C. FutureFuel Corp. produces biobased products, including biofuels, and biobased specialty products. The company also gets A’s in sales growth and free cash flow. For more information, get Portfolio Grader’s complete analysis of FF stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.